The present invention relates to an automatic positioning device mounted on testing equipment or associated tooling devices. In particular, a positioning device is mounted on a gauge fixture or test equipment, the positioning device consisting of two electro-mechanical devices and a controller. The positioning device automatically positions parts to be checked or tested to a high degree of accuracy and repeatability.
The use of positioning devices with equipment, tooling, gauging fixtures and the like for dimensional checking of such parts as automotive glass and sheet metal have been very rudimentary. Predominantly this has been done by hand, where the operator of the gauge fixture will position the part to be checked by line of sight to a scribed line or by feel from his finger tips to a perimeter edge or surface on a gauge fixture. This is very subjective and allows for a tremendous variable in the measurements being taken. A second level of positioning by the operator is to pull or push the part against perimeter stops, this is also subjective, as the operator is unable to assure that the part is in contact with the stops on every part being measured, again measurement data contains large variables. As described in the next paragraph, positioning to a perimeter datum stop also inhibits the full use of the tolerances allowable on the part. A third operator positioning system, made by LMI, provides a visual feed back by way of a needle gauge that the operator reads. This device is simply a differential volt meter utilizing two linear displacement sensors. The LMI system has the fundamental draw back of not being able to be zeroed, that is a reference position is unable to be accurately obtained. The system still relies on the operator to feel the part into position whilst looking at the needle which once again introduces operator variables. The system also does not have the ability to show, or data log how accurately the part is positioned, thus still providing variable positioning and unreliable data collection.
To eliminate operator input, several devices have been used that include pushers that push the part against stops. This particular system when properly executed can provide a consistent positioning of the part, but has the draw back of compromising the perimeter tolerance. This compromise is due to the positioning of the datum stop, which can be at minimum, nominal or maximum size, thus tolerance on the edge of the part placed against the datum, is not being utilized and is accentuated on the opposing side of the part. A second mechanical system is linear actuators, such as air cylinders, that come to a positioning stop at a point near the proposed edge of a perfect part. This positioning system falters because the final positioning of the moveable datum stops can be no closer than what the largest part size would be. Those parts made to less than the largest tolerance size are able to float in position which allows variability in measurements. If the part to be measured is out of tolerance, being too large, the actuated datums will not come to their final position but, will be stopped by the edge of the part. Thus, the location of the part to be measured will be offset from it""s nominal or proposed position on the gauge.
Therefore, a need exists for a system that: (1) automatically positions the part without introducing operator variables; (2) accurately positions the part taking into account part intolerance; (3) achieves high accuracy and repeatability of positioning irrelevant to part size variability; (4) feeds back to the operator or data log the positioning accuracy of the part; (5) self checks if the part is positioned correctly; and (6) if the part is not positioned correctly, automatically repositions or rejects the part from measurement.
Specifically, the automotive glass industry has desired the ability to accurately and repeatedly position windshields and back glass centrally from side to side on gauge fixtures for the purpose of measuring, irrespective of part size accuracy or part to part consistency. This challenge has yet to be met with any degree of accuracy or consistency. One objective of the present invention is to provide such a device.
In accordance with the present invention, an automatic positioning device is disclosed that permits the part being measured to be located accurately, taking into consideration part intolerance, and variability from part to part. This device is also able to automatically check if the part is accurately positioned and either repositions the part if not positioned correctly, or rejects the part from further measurement. This device will also allow a measurement to be taken for operator view or data logging on the accuracy to which the glass has been positioned.
Preferably, electro-mechanical devices in conjunction with a micro-controller and sensors are utilized in a closed loop feed back system to move and dynamically measure the position of the part on the gauge fixture. This allows accurate positioning of the part on the gauge, averaging the intolerance of the part size. The invention includes at least two mechanical devices, a pusher assembly and a positioner assembly which physically move and position the part, and an electronics system which holds the programming that controls the actuation of the pusher assembly and the positioner assembly in positioning of the final part.
The two mechanical devices usually are in a position opposed to each other on the gauge. The first mechanical device, called the pusher, consists of a base plate, air cylinder/pusher and a linear sensor. The second mechanical device, called the positioner consists of a base plate, motor plate, electrical motor, crank, linear sensor and stop. These two devices physically move the part into its centralized or desired position by two separate movements. The pusher assembly initially pushes the part using the air cylinder or similar mechanical means, to the stop on the positioner assembly. This assures that the part is biased toward the positioner assembly, as the stopper is placed outside the maximum part size. Once the pusher has biased the part toward the positioner, the sensors, one on each device, actuate out to sense the offset of the part, which is now biased toward the positioner. The positioner assembly now moves the part in a controlled fashion using the motor and crank back toward the pusher side until the required position is attained. The positioner""s motor and crank could also be a linear ball screw with motor, linear motor or similar actuation device controllable from a micro-controller or similar device.
The electronics system typically is comprised of a micro-controller and motor controller. The micro-controller could also be a computer, PLC or similar device. The micro-controller reads the sensors on both the pusher and positioner once in their actuated position. Therefore, the micro-controller knows the position of the part and the size. The micro-controller then provides the correct amount of power and timing through the motor controller to move the crank and therefore the part. When the sensors read equally or at least to a predetermined setting in the micro-controller, the micro-controller stops the motor, places it in reverse and retracts the crank. To assure that the part is still in position, the micro-controller will check the part utilizing the sensor, if the part is correctly placed the micro-controller will inform the operator through visual indications that the part is ready to take measurements or directly inform data acquisition equipment. If the part is not correctly positioned, the micro-controller can attempt to position it again, or reject the part for inspection. As this is a programmable device, the ability to add variables, change sequences or kinematics to suit part size and type is infinitely variable. Note that the crank could be left in the stopped position and not retracted once the part has reached it""s final position acting as a contact datum stop. As the measurement through the linear sensors is separate to that of the actuation and movement, this provides a true closed loop feedback system providing high accuracy and repeatability.
Through this use, in the present invention, of a combination of a micro-controller, an electro-mechanical positioner assembly and an electro-mechanical pusher assembly, the positioning system can position or centralize a part to be measured on a gauge fixture in a highly accurate and repeatable fashion. This eliminates operator input, increasing efficiency and accuracy. The accuracy and repeatability of the invention has not been attainable by operators or existing mechanical devices. It has been found that the invention can position within 0.002 inches.
There are other attributes of the above invention to accommodate the end user, for cost saving due to maintenance or exchange of components. The plates on both the pusher assembly and positioner assembly are dual plates, where the upper is doweled to the lower. The position of both the pusher and positioner with respect to the datums of the gauge fixture is highly accurate and attained by positioning the lower plate. To allow for removal and replacement, the upper plate on both the pusher and positioner can be unbolted and accurately replaced. This allows for a modular replacement for maintenance or the removal and use elsewhere of the pusher assembly and positioner assembly if the gauge fixture is temporarily out of service.
As this invention is driven by a micro-controller or equivalent device such as a computer or PLC, feedback to the operator through a visual display can be incorporated, allowing the operator or quality engineers to see the accuracy at which the part is being positioned. The electronics can be connected to other automated devices on the gauging fixture, thus automating the complete cycle of checking as well as automatically logging the positioning data to a data base.